"Using the gene-editing tool CRISPR, the scientists were able to introduce a naturally-occurring genetic mutation into the embryos. This mutation, which modifies an immune-cell gene called CCR5, makes humans that carry it resistant to the HIV virus. The researchers were only able to successfully modify four of the 26 embryos targeted, and some of these embryos also acquired unplanned mutations — a side effect that was similarly observed in the research published last year. After the experiments, the embryos were all destroyed within three days' time." ‎· ronin